1. Field of the Invention
In refrigerating cycles so-called thermostatic expansion valves are widely used. Thermostatic expansion valves are designed to control the flow rate of the refrigerant being introduced into an evaporator in accordance with the temperature and pressure of the low-pressure refrigerant exiting the evaporator.
Another possibility to control the flow rate of the refrigerant flowing into the evaporator is to use a so-called supercooling degree-controlled expansion valve, which in contrast to said thermostatic expansion valve detects and controls the degree of supercooling of the high-pressure refrigerant supplied to the evaporator. A supercooling degree-controlled expansion valve performs all required operations at the inlet side of the evaporator without needing any thermostatic equipment or additional temperature or pressure transmitting passages. This is advantageous because a supercooling degree-controlled expansion valve can be made extremely compact.
2. Description of the Related Art
In a supercooling degree-controlled expansion valve disclosed in U.S. Pat. No. 4,324,112 for example, the valve seat is arranged in a high-pressure refrigerant passage through which the refrigerant is supplied to the evaporator and at a location of an upstream side of a restricted portion formed by narrowing an intermediate portion of the refrigerant passage. The valve element for opening and closing the refrigerant passage faces the valve seat and is urged towards the valve seat by urging means from a downstream side. This valve type is structurally simple and compact and yet is capable of controlling the degree of supercooling of the high-pressure refrigerant at a constant level. However, in said known supercooling degree-controlled expansion valves the valve element freely vibrates due to the refrigerant flow and repeatedly collides against its surrounding member thus producing noise.
In high-pressure hydraulic applications it is known to equip, e.g., a relief valve element with a damping piston received in a cylinder chamber to suppress valve rattling. However, supercooling degree-controlled expansion valves need to operate reliably, extremely sensitive and in an environment (most often in the motor compartment of a vehicle) where permanently external vibration and considerable temperature changes occur. For this reason it was believed that the performance of such supercooling degree-controlled expansion valves would unduly suffer when implementing any vibration attenuating measures.